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La secuenciación del padlet demuestra precisa organización y el diseño de tareas variadas para cada tipo de estilo de aprendizaje denota pensar en las diferentes oportunidades generadas para la diversidad de alumnos para adquirir los contenidos.

Explicar las tareas de modo detallado y conciso lleva al alumno a alcanzar un aprendizaje seguro al final de la secuenciación de las tareas. Interesante llevar a una feria técnica las producciones de los alumnos como cierre final del tema.

Como sugerencia, seria necesario incluir una grilla o rúbrica para que los alumnos se autoevalúen a lo largo del proceso de aprendizaje y puedan hacer preguntas o dejar comentarios para que el alumno mejore su participación clase tras clase y para que la docente mejore la calidad de su practica.

¡BIEN HECHO!

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LLEVAMOS LA TEORIA A LA PRACTICA ...EN LA "EDUTECNO" 

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LLEVAMOS LA TEORIA A LA PRACTICA ...EN LA "EDUTECNO" 

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Realiza una maqueta y un folleto explicativo donde se evidencien los beneficios y usos del sistema de la energia termica en el ambito domestico.
Se les solicitara ayuda a los docentes de taller para la fabricacion y armado del termotanque solar, y posteriormente se expondra durante los dos dias que se extiende la feria para socializarlo a toda la comunidad.

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6) Resolve el siguiente Verdadero/ Falso. Corregi las oraciones falsas, ayudandote con todo el material provisto.

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Direct System
Also called an "active" or "open loop" system, this is the type of system most often installed in the central and southern areas of Florida, and other non-freezing sunbelt climates within the United States.

In the direct system, an electronic control system [1] compares the temperature of a sensor [2] located at the solar collector [6] with the temperature of a sensor [3] located in the bottom of the hot water storage tank [4] (where the coldest water is located). When the solar collector temperature is warmer than the water in the bottom of the tank by some predetermined difference (four degrees, for example), the electronic control turns on a small pump [5], that draws cold water from the bottom of the hot water storage tank and circulates it through the solar collector. Solar heated water is returned to the top of the tank.

The circulating pump is very small and typically uses about the same amount of electricity as a 100-watt lightbulb. Another version of this system uses a small photovoltaic (solar electric) panel to operate a direct current (DC) circulating pump.

Advantages. The direct system typically produces the highest operating efficiency because there is no nighttime heat loss from hot water stored on the roof; nor is any efficiency lost through a heat exchange process. Potable water from the hot water storage tank is circulated directly through the collector.

Disadvantages. The only disadvantage of this system is that freeze protection is provided by circulating warm tank water through the collector. This is not a desirable method of freeze protection in climates that experience more than a day or two of freezing weather each year, because energy loss during freezing weather could be significant. Even more important, freezing weather can coincide with a power outage, preventing the pump from circulating warm water through the solar collector.[1]

ICS System
Integral collector storage systems, also called "batch" solar heaters, combine the hot water storage tank and the solar collector surface into a single component, eliminating the need for circulating pumps or automatic control systems. In its most simple implementation, a water storage tank painted black and sitting out in the sunlight is a rudimentary ICS system.

This type of system works best as a preheater for a conventional or tankless water heater. The cold water line that feeds the conventional water heater is diverted [1] and sent first through the ICS solar module [2]. Circulation is provided by utility mains pressure. In other words, when hot water is drawn out for use from the conventional water heater [3], the storage tank is replenished with solar heated water instead of cold water. This allows the electric or gas heater to work substantially less.

Advantages. The biggest advantage is simplicity: the system has no pumps, no temperature sensors, no electronic controls and no heat exchanger. When combined with a tankless water heater, the system can free up five to six square feet of floor space by eliminating the conventional water heater storage tank.

Disadvantages. The biggest disadvantage is nighttime heat loss. Stored heat is lost through the glass cover plate at night, which of necessity cannot be insulated to prevent heat loss. However, this heat loss is reduced in advanced ICS systems by stretching a thin clear film just underneath the glass cover plate, which creates an insulating air gap. Also, while the greater thermal mass of stored hot water within an ICS solar module makes this type of system more freeze resistant than the direct system (above), ICS systems are not appropriate for climates that experience more than four to five freezing nights per year.

Drain Back System
Drainback systems have a few more components, but are specifically designed to provide fail-safe operation in climates with frequent freezing during the coldest winter weather. The solar collector and control system are the same as the direct circulation system. However, an antifreeze solution is circulated through the solar collector and back into a heat exchanger in the hot water storage tank. The addition of a heat exchanger adds to the cost of the system and creates some degree of heat transfer energy loss, and this combined with the fact that these systems are typically installed at higher latitudes, where incoming solar radiation is reduced, makes indirect solar water heating less viable than its direct circulation cousin.

Like the direct system, an electronic control system [1] compares the temperature of a sensor [2] located at the solar collector [6] with the temperature of a sensor [3] located in the bottom of the hot water storage tank [4] (where the coldest water is located). When the solar collector temperature is warmer than the water in the bottom of the tank by some predetermined difference (four degrees, for example), the electronic control turns on a small pump [5]... However, in the drainback system, the fluid circulating throught the solar collector is separated from the potable water in the hot water storage tank [4].

Either water or a glycol solution is circulated through the solar collector and a drainback tank [7]. When the pump stops, fluid in the solar collector "drains back" into the drainback tank, leaving the solar collector empty whenever it has no fluid circulating through it. A second circulating pump [8] circulates potable water from the hot water storage tank through a heat exchanger in the drainback tank.

In an alternative design, only one pump is required-in the drainback-solar collector loop. In this arrangement, the heat exchanger is typically "wrapped around" the hot water storage tank.

Advantages. The system is designed to fail-safe and drain the solar collector(s) during freezing weather, even if a power failure should occur.

Disadvantages. The heat exchanger makes this system slightly less efficient than a direct system. And as you might expect, the drainback tank, second pump and heat exchanger make this system a bit more expensive than an ICS or direct system with comparable solar collector area and hot water storage capacity. On the other hand, this system is ideally suited to climates that may experience 10 or more days of freezing weather per year.

Thermosyphon System
This type of system is the most common in Japan, Israel and Australia, which have enjoyed an installed base of millions of residential and commercial systems for the last 30 years.[2] Like the ICS system, the thermosyphon system eliminates the circulation and control system.

However, circulation is provided by the thermosyphoning principle: The hot water storage tank is located higher than the solar collector and circulation flow is induced when the coldest water in the bottom of the storage tank falls by gravity through a circulation line into the bottom of the solar collector panel, where it is heated and rises. Water heated in the solar collector panel rises into a circulation line to a high point in the water storage tank.

Advantages. Unlike the ICS system, which combines hot water storage with energy collection and so can lose heat at night through its glass cover plate, the thermosyphon system optimizes system efficiency by fully insulating a separate storage tank.

Disadvantages. The thermosyphon system's primary drawback is appearance: The hot water storage tank must be higher than the solar collector, so it becomes a bulky protrusion on the roof. Modern thermosyphon systems place the tank on its side, along the top edge of the solar collector panel (see the photo), but while modern solar water heating collectors look like skylights, many homeowners are resistant to the idea of a tank on their roof.

An additional concern is weight: While the ICS system spreads its hot water storage over a greater roof area, the weight in a thermosyphon system storage tank is usually more concentrated. An older roof structure may not be able to support the added weight of a hot water storage tank.[3]

Why not use solar electric power for water heating?
This is an excellent question. Understanding the answer provides some insight into why, 50 to 100 years from now, solar water heaters will still be the best way to heat water.

And why you should go ahead and install a solar water heater today?
The issue is conversion efficiency. A typical flat plate solar water heating collector transfers about 63 percent of the solar energy that strikes it directly into the water (or heat transfer fluid, in indirect circulation systems).

A typical photovoltaic (PV) solar electric cell converts only 15 percent or so of the energy striking it into electrical energy under ideal conditions: PV cells lose efficiency as operating temperatures rise. Additional inefficiency occurs when an inverter changes direct solar electric current (DC) into alternating current (AC). The end result is that a PV cell with a 15 percent rated peak efficiency only delivers about 10 percent of the energy striking its surface to a demand load.

So here is the problem: The solar electric PV panels would require more than six times the roof area of a flat plate solar thermal collector to meet the same (water heating) demand load.

Meeting the hot water needs of an average Florida family of four requires about 40 square feet of flat plate solar water heating collector surface area, so to do the same job with PV panels would take about 40 x 6 = 240 square feet of PV panel surface area.

References and Notes
The best freeze protection in a sunbelt climate with very rare freezing weather is to manually drain the solar collector: Turn off the gate valves on the circulating lines that connect the solar collector to the hot water storage tank, attach a garden hose to a drain spigot on the solar feed line and open the spigot to drain water out of the solar collector. The solar loop gate valves and drain spigot are usually located just above the hot water storage tank.

Roughly half of all Florida homes had thermosyphon solar water heaters during the 1940s, with an estimated 60,000 systems in Miami.

Thermosyphon system solar collectors were often separated from the hot water storage tank in old Florida "Cracker" homes. The tank was typically installed in the attic in an upright position, often in the center of the space under the peak of the roof. The solar collector panel was located at a lower point on the roof so the collector panel inlet was lower than the bottom of the hot water storage tank

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Different Solar Water Heating System Types

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Direct System Also called an "active" or "open loop" system, this is the type of system most often installed in the central and southern areas of Florida, and other non-freezing sunbelt climates within the United States.

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thermal energy

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Solar water heating collectors capture and retain heat from the sun and transfer this heat to a liquid. Solar thermal heat is trapped using the "greenhouse effect," in this case is the ability of a reflective surface to transmit short wave radiation and reflect long wave radiation. Heat and infrared radiation (IR) are produced when short wave radiation light hits a collector's absorber, which is then trapped inside the collector. Fluid, usually water, in contact with the absorber collects the trapped heat to transfer it to storage.

Two principles govern solar thermal collectors. First, any hot object eventually looses its heat back to the environment. The efficiency of a solar thermal collector is directly related to heat loss, mainly from convection and radiation. Thermal insulation is used to slow down heat loss from a hot object to its environment.

Second, heat loss is more rapid if the temperature difference between a hot object and its environment is larger, in this case between the temperature of the collector surface and the ambient temperature. (But the same goes for transferring heat from the collector to the fluid, a larger difference between the collector and the liquid, the more heat is transferred.)

The most basic approach to solar heating of water is to simply put a tank filled with water into the sun. The heat from the sun would heat the metal tank and the water inside. This was how the very first SWH systems worked more than a century ago. However, this setup would be inefficient because there is little to limit the heat loss from the tank. Adding an insulated box around the tank, and adding glass above the top where the sun comes in would do a lot to retain heat.

A more common collector is called a flat plate collector. It has a large, flat surface area (absorber) to maximize exposure to the sun, and has small tubes bonded to it. Fluid runs through the tubes, collecting the heat from the absorber. The sides and bottom of the collector are well-insulated, and glass on top completes the insulation.

This is quite simple, but there are some very technical factors involved in making the collector as efficient as possible. One is the coating on the absorber, which is specially formulated to both absorb as much heat as possible, and to radiate back out as little heat as possible. Another is the glass, which is high-iron and specially coated to let as much light energy as possible through and to also prevent as much heat loss as possible.

Another popular type of collector is called evacuated tube, which has a long, skinny absorber that is inside a glass tube. The tube has the air evacuated out of it, which makes it highly insulated-not too different from a thermos used to keep drinks hot.

The final type of collector is a parabolic dish or tray, which increases heat potential by concentrating sunlight onto a small absorber. These are very rare in home water heating systems, and more commonly used in utility-scale systems to create steam which runs turbines to make electricity.

The basic components in home solar heating systems include:

Collectors to take the heat from the sun and pass it to a fluid

The heat transfer fluid which takes the heat from the collector for use or storage

Heat exchangers to transfer the heat from the fluid to a home's domestic water.

Pumps to move the fluid through the collector and/or the exchanger, and sometimes to move the domestic water through the other side of the exchanger.

Controllers to run the pumps when there is collector heat available.

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Solar Water Heating System Basics | Home Power Magazine

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Solar water heating collectors capture and retain heat from the sun and transfer this heat to a liquid. Solar thermal heat is trapped using the "greenhouse effect," in this case is the ability of a reflective surface to transmit short wave radiation and reflect long wave radiation.

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Solar energy, solar power derived from the sun through the use of solar panels, is just one of the newest initiatives the "Going Green" movement has presented to us, in an effort to build and maintain renewable and sustainable power sources. As with any new addition to your home, there is always the initial cost of the components and installation cost to get it up and running.

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The 10 Best Ways You Can Use Solar Energy in Your Home

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Solar energy, solar power derived from the sun through the use of solar panels, is just one of the newest initiatives the "Going Green" movement has presented to us, in an effort to build and maintain renewable and sustainable power sources.

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5) Lee y mira el video una vez mas para armar el rompecabezas que explica el funcionamiento del sistema.

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4) Observa el siguiente esquema del sistema y busca sus partes en el diccionario online "Word Reference"

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DICTIONARY WORK- LABEL PARTS OF THE SYSTEM.doc

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1) Lee el siguiente texto acerca del sistema de energia solar y su uso domestico.

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3) Observa el siguiente video y responde las preguntas:
a) ¿Como ingresa el agua al tanque?
b) ¿Cual es la funcion del panel?
c) ¿Como es el proceso de calentamiento?
d) ¿Cual es la funcion de cada una de las partes del sistema?

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2) Lee nuevamente y encierra la opcion correcta, segun el contexto en que se hallan dichas palabras.

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"WATER SOLAR HEATER SYSTEM": Energia Solar Termica para agua caliente sanitaria

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"WATER SOLAR HEATER SYSTEM": Energia Solar Termica para agua caliente sanitaria

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Un E- Portafolio es una coleccion de trabajos personales que da cuenta del desarrollo de competencias y habilidades socio-culturales y cognitivas a lo largo del proceso de aprendizaje.

¿Cual es el proposito de emplear este tipo de portafolio?

Se utiliza como herramienta para desarrollar el pensamiento critico y reflexivo sobre las propias practicas personales. Por su parte, el portafolio constituye una herramienta para la evaluacion del docente hacia el alumno y la autoevaluacion.